Abstract:

Alkali metals have detrimental effects on fast pyrolysis process for bio crude. In this thesis, a new process for the removal of these alkalis was designed. In this way, the yield, quality and profitability of pyrolysis process could be enhanced.

The design of the unit included testing the wash process in laboratory and pilot scale, choosing the suitable equipment, drawing the flow chart including the control instruments, writing the operating instructions, calculating the mass balances, defining the technical values for the equipment. The economic potential of the unit was studied by searching the current prices for the equipment, calculating the fixed capital investment and the operating costs based on the balances and power consumption of equipment and comparing these to the grown sale incomes. Sensitivity analysis was performed for the fixed capital investment and the prices of chemicals: nitric acid and sodium hydroxide.

In this Thesis, a process including the following phases was designed: The forest residue biomass is crushed into a finer particle size (to <5 mm), washed with 40 °C 1 % nitric acid (1:5), solid is separated with vacuum in a rotary vacuum drum washer, rinsed with 40 °C water (1:5), pressed with a mechanical press to remove the residual water and the used acid is neutralized by sodium hydroxide. Water is recycled by reverse osmosis, which separates the salts. The waste water is led to the municipal waste water treatment plant.

The goal of the washing process is to reduce the ash content of the forest residue to the level of trunk tree. The goal was achieved in laboratory scale and fairly in the pilot scale experiment. The ash removal efficiency was 50 % in laboratory and 45 % in pilot scale. However, the pyrolysis experiment showed that the bio-oil yield was only slightly increased, when the washed biomass was used instead of the regular forest residue. At the moment, this process does not have economic potential without major modifications and further study.Alkalimetallit vaikuttavat nopeapyrolyysiprosessiin haitallisesti. Tässä työssä suunniteltiin prosessi, jolla poistetaan alkalimetalleja biomassasta. Näin voitaisiin parantaa varsinaisen pyrolyysiprosessin kannattavuutta ja nostaa tuotteen laatua.